There's "nothing" about Mary that is entertaining. Stiller and Diaz are the main characters. It's a bit of romance, allegedly, but if you're looking for inspiration or chemistry or charm, forget it. Still, there's nothing wrong with the story. It's just dull. The guy goes on a bit of an odyssey, and the only funny part of the movie is a bit where he stumbles at a rest stop where the police turn on their lights and see a hoard of men engaging in sexual activity with each other. That was pretty funny. Not hilarious, but funny. The rest of the movie is not even dry humor. It's weak romance. But, since it's about ordinary people, I guess it passes for someone who doesn't have any attention deficit disorder at all.